Im so sorry for your loss, quasi and I send my condolences and all the love to your family.
Personally, I believe when we lose people it is only here in this physical plane. I believe souls and energy live on in the people who remember and love them. She is with you always as well as the lessons you learned from her. Everyone has a greater purpose and once they meet it, they are called home to All That Is. I've dealt with many a death and great loss of family members by believing its never goodbye, rather a See You Later. The love you have for her will carry you through the grief. Whatever you wish she knew, say it out loud, put it out into the Universe...that soul connection you have with her will carry that message forward.
Dont hold on to regret for the things not said, you are exactly where you need to be right now in your life for a reason. As tragic as it is, sometimes we need the hard lessons to teach us how to love one another better.
Lots of love to you and your family